With findings suggesting that male circumcision reduces risk of HIV acquisition for men, researchers now are turning attention on circumcision's impact on acquisition of sexually transmitted disease (STD) for women. Findings presented at the recent International Society for Sexually Transmitted Diseases Research in Seattle indicate that the protective effect of male circumcision may not transfer to STD risk reduction in female sexual partners.1

An international expert consultation was convened in March 2007 by the World Health Organization (WHO) and the UNAIDS Secretariat, with a recommendation issued that male circumcision be recognized as an additional important intervention to reduce the risk of heterosexually acquired HIV infection in men. The consultation was held following publication of evidence from three randomized controlled trials undertaken in Kisumu, Kenya; Rakai District, Uganda; and Orange Farm, South Africa, that male circumcision reduces the risk of heterosexually acquired HIV infection in men by about 60%.2-4

In contrast to HIV, the effects of circumcision on other sexually transmitted infections have been studied much less, states William Miller, MD, PhD, MPH, associate professor of medicine and epidemiology at the University of North Carolina at Chapel Hill. Miller and fellow researchers analyzed data from a prospective cohort study on hormonal contraception and incident HIV and STDs conducted among women from Uganda, Zimbabwe, and Thailand for the report presented at the Seattle conference.

"We felt that there was the potential that circumcision could also reduce a woman's risk for acquiring these other STIs," says Miller of the report's genesis. "The mechanism could either be through reducing men's risk, which would secondarily reduce women's risk, or alternatively, there could be reduced transmission associated with circumcision, perhaps through effects on organism burden."

The report's findings indicate that male circumcision was not associated with women's risk of acquisition of gonococcal or trichomonal infections. Circumcision had no effect on chlamydia when all participants were considered together; however, when analysis was restricted to monogamous women, those with circumcised partners appeared to have increased risk for chlamydial infection.1

Miller's study was done as a secondary data analysis, he says. "I would think that a study specifically designed to assess this relationship would have a better chance of identifying any protective — or even increased risk — relationship," Miller says. "Furthermore, I think that as programs are developed for circumcision to prevent HIV infection, the potential consequences and/or benefits for women should be carefully monitored."

Review the results

To perform the study on women's risk of chlamydial, gonococcal, and trichomonal infections, scientists looked at 5,925 women from Uganda, Zimbabwe, and Thailand who were seen quarterly for up to two years. The women underwent physical exams with specimen collection and were given face-to-face questionnaires to gather sexual and behavioral data.

Women were asked about the circumcision status of their partners: 18.6% reported a circumcised primary partner at baseline, 70.8% reported an uncircumcised partner, and 9.7% did not know their partner's circumcision status. During follow-up, 411, 307, and 373 participants had a first incident chlamydial, gonococcal, or trichomonal infection, respectively.

In multivariate analysis, after controlling for contraceptive method, age, age at coital debut, and country, the adjusted hazard ratio (HR) comparing women with circumcised partners to those with uncircumcised partners for chlamydia was 1.22 [95% confidence interval (CI): 0.94 to 1.59]; for gonorrhea, adjusted HR: 0.93 (95% CI: 0.70 to 1.24); for trichomoniasis, adjusted HR: 1.05 (95% CI: 0.81 to 1.37), and for all three infections combined, adjusted HR: 1.02 (95% CI: 0.86 to 1.22). Sensitivity analysis excluding women reporting multiple sexual partners had little influence on the estimates for gonorrhea and trichomoniasis; however, for chlamydia, analyses restricted to women with only one sexual partner revealed those with circumcised partners had increased risk of acquisition compared to participants with uncircumcised partners (restricted HR: 1.33, 95% CI: 1.01 to 1.75).1

Further research should be aimed at determining male circumcision's potential effects of genital ulcer diseases, such as chancroid, herpes, syphilis, and human papillomavirus (HPV), says King Holmes, MD, PhD, director of the Center for AIDS and Sexually Transmitted Diseases at the University of Washington in Seattle. Skin-to-skin transmission routes may be the link to any protective effect, he observes.

For example, earlier research has indicated that women whose male partners were uncircumcised were more likely to acquire/develop cervical cancer,5 says Holmes. Does this mean that men who don't have a foreskin are more likely to acquire or transmit HPV? Such a hypothesis remains to be fully tested in future studies, he notes.

Hypothesis on circumcision

Results of a meta-analysis presented at the Seattle conference indicate that male circumcision is associated with a reduced risk of symptomatic genital ulcer disease.6 The report, based on a meta-analysis of observational studies and one randomized trial, hypothesizes that while the protective effect may be due to a reduction in infection with ulcerative STDs, it also is possible that circumcision reduces the frequency and duration of symptoms. This reduction in infection may contribute to reduced acquisition of HIV infection found in circumcised men, the report concludes.6

Another area of potential research lies in determining male circumcision's impact on bacterial vaginosis (BV), says Holmes. Scientists have speculated that the bacteria that cause BV can survive under the foreskin of an uncircumcised man, observes Holmes. A man with multiple partners may be more likely to transmit infection to an uninfected partner by just transporting the bacteria he has acquired from the woman who has the infection, he notes. Findings indicate circumcision may have a protective effect. A statistical review of the past medical files of more than 300 couples in Uganda, where the female partner was HIV-negative and the male was HIV-positive, indicates that male circumcision reduced rates of trichomonas and bacterial vaginosis in female partners.7

Does male circumcision extend its protective effect to women when it comes to HIV? Researchers at Johns Hopkins University in Baltimore currently have an ongoing trial to answer that question. The study will not be completed until 2008.